LS Engines 101: An Introductory Overview of the Gen III/IV LS Engine Family

This LS engine was swapped from a Corvette into a ’69 Camaro, which in the LS-swapping universe, isn’t anywhere close to unusual. (Image/Pinterest)

(Updated 10/09/2018)

[Editor’s Note: You can find a comprehensive list of every LS and Vortec engine spec guide and upgrade guide we’ve published to date by scrolling to the bottom of this article.]

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Chevrolet introduced the automotive world to the LS engine with the launch of the LS1 in the 1997 Corvette C5.

It left a mark.

The lightweight engine made big-block horsepower in a package no bigger than the engine-swapping community’s previous hero—the small block Chevy. Not only did the LS engine platform provide opportunity for making unprecedented power in a small-block mill, it did so while meeting modern fuel economy and emission standards.

In an automotive context, it’s not hyperbole to say the LS engine changed the world.

Because LS blocks share similar exterior dimensions, the vast majority of LS engines can fit anywhere that a small block Chevy 350 can. They’re ideal for both tame daily driver builds, as well as high-performance street or race applications north of 1,000 horsepower.

We know you get it—LS engines are really popular. Even better—they’re pretty easy to find. Both factory and aftermarket LS parts are readily available. And dropping an LS motor into another vehicle—particularly any car or truck previously powered by a small block Chevy—is as simple as engine swapping gets.

As is often the case, the devil tends to be in the details. So we’re going to deliver those details, and we’re not going to take anything for granted in the process.

There are several engines within the LS family. So if you’re going to swap or modify an LS, the first thing you’ll need to know is which particular engine you have or want, and how to find it (should you choose to not go with one of the many LS crate enginesavailable). That means understanding the various technical nuances of each LS RPO code, so you know which new parts to buy, or what old parts to salvage on your next trip to the junkyard.

Know Your LS Engines

(Image/Pinterest)

Even among experienced mechanics and auto enthusiasts, there is a lot of confusion about General Motors’ naming convention for the LS engine series. We’re going to clear up as much uncertainty as we can.

1. It Doesn’t Have to Say “LS” to be an LS Engine (Hello, Vortec)

It was automotive enthusiasts who gave the “LS Engine Series” its name.

Officially, there’s no such thing. What we call the LS engine series is really just all of the engines from General Motors’ Gen III and Gen IV small-block V8 groups.

If you want, you can imagine the LS engine series kind of like a group of celebrities—people like Oprah Winfrey and Ben Affleck—who were given honorary doctorates from Ivy League universities, and then afterward everyone actually started calling them Dr. Winfrey and Dr. Affleck.

“Congratulations, Dr. Affleck. I thought you were amazing in Gigli, and your interpretation of Batman is definitely just as good as Christian Bale’s,” the president of Brown University probably said.

Much like that very realistic scenario, Chevy’s L76 and L77 engines are actually LS engines.

And though the majority of people might call them Vortec engines, GM’s small-block 4.8L, 5.3L, 6.0L, and 6.2L truck engines from 1997 through Gen IV are still very much members of the LS engine family.

The LS1 was the first mill from GM’s Gen III small-block engine platform. Then, the 385-hp LS6 made its appearance in the 2001 Corvette Z06, and everyone just sort of latched onto the “LS series” name.

But if we’re going by the book (and we’re not—we just want you to get it), the LS1 and LS6 are just two of several Regular Production Option (RPO) codes in GM’s Gen III engine book.

In fact, there have already been LS engines—the original Chevy 454, for example. It was introduced in 1970 and came in three variants: the LS5 (an RPO code you won’t find in the modern LS family), the LS6, and the LS7. So, if you’re one of the people who think it’s all a little confusing, you’re not weird. It’s actually confusing and you probably don’t need a lobotomy.

There are at least 25 RPO codes within the LS engine platform that don’t contain the letters “LS” at all (though they do all begin with the letter L). You’ll find the full list below in our LS Engine Family Tree.

2. The LS Engines Were Not Released in Sequential Numerical Order

This should be obvious if you paid attention to that last note. But it might bear repeating. Even though it would make sense to the majority of people, GM didn’t release the LS2 immediately after the LS1. That would have made it too easy. The LS6 came next.

But GM also launched two LS truck engines before unleashing the LS6—the 4.8L Vortec (LR4) and the 5.3L Vortec (LM7, L59, LM4, L33). Sometimes, the only differentiator between these engines is the block material: cast iron or aluminum—another subject we’ll dive into further as we explore the LS engine universe.

3. ‘Wait a Minute… We Can Use Easy-to-Find Truck LS Engines for Swaps?’

Yep. Fun, right?

But there are all sorts of Ifs, Ands, and Buts to think about, depending on your specific application. We’ll tell you as much as we can. Near the bottom of this article, you’ll find a still-growing list of LS and LS-based truck engine specification guides and comprehensive engine upgrade guides. These guides are full of all kinds of expert LS-engine wisdom, courtesy of our friends at Summit Racing.

4. One of These Things is Not Like the Others (Spoiler: It’s the LS4)

The LS4 is the oddball of the LS series. There’s a VERY good chance that it’s not your friend and will openly mock that Def Leppard poster you have hanging in your garage.

The LS4 is designed specifically for transverse front-wheel drive applications, unlike every other LS-based RPO code. Unless you like to fabricate (a lot!), you’ll probably save yourself trouble by steering clear of the LS4.

You’ll sound silly AND get the wrong parts—two things best avoided. We have it on good authority that several people refer to ANY LS engine from the third generation of Chevy small blocks as an “LS1.” It would be helpful to everyone in the world if that stopped happening.

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The lifetime of the LS engine series can be split in two halves—Gen III and Gen IV. Gen III spanned from 1996 to 2007. And Gen IV spans from 2005 through today. With the all-new Gen V 6.2L LT1 (released for the C7 2014 Corvette Stingray), new LS engine production could be nearing its end, but we assure you that people using LS powerplants to make their vehicles go won’t stop for a very long time.

To wrap your head around the group of engines that make up the LS engine family, we think it’s helpful to understand the architecture of the LS family tree, so we’re going show you how that looks.

The LS Engine Family Tree

Forgive us for not making it actually look very family tree-like. But this is a high-level look at the LS engine family that you might find useful.

LS engine blocks are either cast iron or aluminum. All car engines had aluminum blocks. Truck engines could be either material.

With the noted exception of the early LQ4 engine, all LS engines have aluminum cylinder heads.

The LS2 and L76 are noteworthy in that they are both Gen IV 6.0L aluminum block engines, and that they came from the factory in both cars and trucks. Each came with different accessory drives, intake manifolds, and oil pans. They also had different VIN codes.

The LS364 is a carbureted Gen IV crate engine GM makes exclusively for the aftermarket.

58 Comments

Sorry guys – but the LS Truck engines (4.8L, 5.3L, and 6.0L) didn’t start until 1999 – in the new GM Pickup Trucks (GMT-800s). 1997 was the Vette only (LS1) and 1998 was the Vette and the F-Car (Camaro/Firebird) – again LS1 aluminum block 5.7L only for the first two years 97 & 98. And I think these early LS1 blocks can only be bored 0.010″ over – the casting walls are thin.

We didn’t mean to suggest otherwise, but the “launched at the same time as the LS1” is imprecise and is technically inaccurate, as you said. That particular section was dedicated to helping people only loosely familiar with LS engines understand that the engines didn’t release in sequential numerical order. Those truck engines were the next LS-based engines to come out when it was just the LS1 before the LS6 in ’01.

We’ll adjust the sentence to be more precise. Thank you for reading the story and taking time to share that info, all of which is spot on.